How big is a mature egg?

If a woman wants to do a vaginal ultrasound to detect the growth and development of eggs, the normal size of mature eggs is about 1.8~2cm, and normal eggs grow to about 2cm, will naturally rupture from the ovary and then be picked up by the umbrella end of the fallopian tube. If sperm enters at this time, it may combine with the egg to form a fertilized egg, thus causing a woman to become pregnant. But for some women with abnormal ovulation function, only small eggs may grow, but no mature eggs are discharged. Such women cannot successfully conceive, and women may often show infertility.